sedimentary

Chert (Nodule)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Tan, brown, grey, yellowish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic), trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: Tan, brown, grey, yellowish
Luster: Waxy to dull

Identified May 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater within sedimentary host rocks like limestone or chalk. Commonly found in Mesozoic or Paleozoic strata.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to conchoidal fracture which creates sharp edges. Currently used in construction aggregate and as decorative landscaping stones.

Geological facts

Chert was one of the most important raw materials for early humans; it is chemically identical to flint, but 'flint' is a term usually reserved for chert found specifically in chalk deposits.

Field identification & locations

Identify by its waxy appearance, extreme hardness (can scratch glass/steel), and smooth, curved shell-like fracture surfaces. Often found as rounded nodules in streambeds or weathered out of limestone cliffs.